1. Field of the Invention
The present invention relates to a removable disk cartridge and to a data storage device for receiving same. More particularly, the present invention relates to methods and apparatus for detecting the presence of the disk cartridge in the data storage device, and to a data storage device and disk cartridge adapted for use in the data storage device having means for protecting against the insertion of incompatible disk cartridges in the device.
2. Description of the Prior Art
Removable disk cartridges for storing digital electronic information typically comprise an outer casing or shell that houses a rotatable recording medium, or disk, upon which electronic information can be stored. The cartridge shell often comprises upper and lower halves that are joined together to house the disk. The disk is mounted on a hub that rotates freely within the cartridge. When the cartridge is inserted into a disk drive, a spindle motor in the drive engages with the disk hub in order to rotate the disk within the cartridge. The outer shell of the cartridge typically has some form of opening near its forward edge to provide the recording heads of the drive with access to the recording surfaces of the disk. A shutter or door mechanism is often provided to cover the opening when the cartridge is not in use to prevent dust or other contaminants from entering the cartridge and settling on the recording surface of the disk.
Disk drives for receiving removable disk cartridges, including conventional 3.5" floppy disk drives, must have some mechanism for detecting the insertion or presence of a disk cartridge in the drive. The actuator that carries the recording heads of the disk drive across the recording surfaces of the disk should not be allowed to move unless the presence of a disk cartridge is detected. In the prior art, mechanical switches are typically employed to detect the presence of a disk cartridge within the drive. Such switches are typically positioned such that when a disk cartridge is inserted fully into the drive, the cartridge contacts the switch, thereby providing an indication that the disk cartridge is present.
One problem with these prior art techniques is that the switch(es) used to detect the presence of a disk cartridge can be activated by foreign objects inserted into the drive, such as pencils, pens or other objects accidentally or deliberately inserted into the drive. As a result, the drive may assume that a disk cartridge is present and therefore release the actuator that carries the recording heads of the drive allowing the heads to move outward into the interior space of the drive. Damage to the recording heads of the drive can result from the heads colliding with any such foreign objects. Additionally, in disk drives that employ opposed heads that rely on the presence of a rotating recording medium to keep them apart, the heads could be damaged by colliding with themselves. Another disadvantage of using mechanical switches and the like to detect the presence of a disk cartridge is that the switches and associated hardware components increase the complexity of the disk drive, creating a greater risk of malfunction and increasing the cost of the drive. As the foregoing illustrates, there is a need for improved methods and apparatus for detecting the presence of a disk cartridge in a disk drive.
Another disadvantage of many prior art disk drives is that the insertion of incompatible disk cartridges in such a drive, i.e., cartridges not specifically intended for use in the drive, can initiate certain critical functions of the disk drive upon insertion into the drive. For example, an incompatible cartridge could cause the heads of the disk drive to "unlock" and potentially collide with the front of the incompatible cartridge causing damage. Additionally, the incompatible cartridge could cause the spindle motor of the disk drive to spin-up to speed, possibly causing further damage. Unlocking of the heads and rotation of the spindle motor should only be permitted when a disk cartridge specifically designed for use with the disk drive is properly inserted in the disk drive. Otherwise, damage to the disk drive spindle motor and read/write heads can occur. Accordingly, there is a further need for a disk drive, and a disk cartridge specifically adapted for use in the disk drive, that do not permit operation of these critical functions when an incompatible disk cartridge is inserted in the disk drive.
The methods and apparatus of the present invention satisfy the foregoing needs.